Ingo Molnar wrote:
* Andrew Morton <[email protected]> wrote:
On Tue, 30 Jan 2007 14:56:16 -0000
Avi Kivity <[email protected]> wrote:
+static void decache_vcpus_on_cpu(int cpu)
+{
+ struct kvm *vm;
+ struct kvm_vcpu *vcpu;
+ int i;
+
+ spin_lock(&kvm_lock);
+ list_for_each_entry(vm, &vm_list, vm_list)
+ for (i = 0; i < KVM_MAX_VCPUS; ++i) {
+ vcpu = &vm->vcpus[i];
+ /*
+ * If the vcpu is locked, then it is running on some
+ * other cpu and therefore it is not cached on the
+ * cpu in question.
+ *
+ * If it's not locked, check the last cpu it executed
+ * on.
+ */
+ if (mutex_trylock(&vcpu->mutex)) {
+ if (vcpu->cpu == cpu) {
+ kvm_arch_ops->vcpu_decache(vcpu);
+ vcpu->cpu = -1;
+ }
+ mutex_unlock(&vcpu->mutex);
+ }
+ }
+ spin_unlock(&kvm_lock);
+}
The trylock is unpleasing. Perhaps kvm_lock should be a mutex or
something?
this is a special case. The vcpu->mutex acts as a 'this vcpu is running
right now' flag as well - hence the trylock signals: is it running right
now or not - if it's not running we do not have to 'decache' it. But i
agree and i already suggested to Avi to change kvm_lock to be a mutex -
but this wont change the trylock.
To elaborate a little: replacing mutex_trylock() with mutex_lock() will
cause unbounded latency as we wait for the vcpu to be descheduled. In
this case, we're only interested in descheduled vcpus, so there's no
need to wait.
kvm is a bit funny in how it likes to pin cpus.
--
error compiling committee.c: too many arguments to function
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